


Day 11: Deep Water (Ocean)

by WatermelonTuesdays



Series: Sheith Monster Fuckers 2019 [11]
Category: Voltron: Legendary Defender
Genre: Alternate Universe - Merpeople, Blind Keith (Voltron), Bondage, Bottom Shiro (Voltron), Consensual Tentacles, Explicit Consent, M/M, Mer-Octopus Keith, Restraints, Sex, Tentacle Sex, Tentacles, Top Keith (Voltron), Weird Biology, glow-in-the-dark tentacles, mer shiro
Language: English
Status: Completed
Published: 2019-10-11
Updated: 2019-10-11
Packaged: 2020-12-09 09:48:53
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,072
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20992805
Author URL: https://archiveofourown.org/users/WatermelonTuesdays/pseuds/WatermelonTuesdays
Summary: Mer-Shiro goes down to the dark waters to meet with his Octo-mer boyfriend Keith. Things escalate rather quickly, and I do mean tentacles.





	Day 11: Deep Water (Ocean)

Shiro had always been warned about the deep waters and the terrors that lurk in the dark. It’s not about what you see, he was told, it’s about what you don’t see. Curiosity kills the cat(fish). But Shiro had always been curious, and too brave to know what’s good for him, so he had flipped his fins at the warnings and swam as far as he could. 

As a child, he didn’t make it far. He dove until the water grew dim and cloudy before the fear and the water pressure overtook him and he raced back to his home coral. The next year he was braver, and he was braver still the year after that, and the one after that. 

His fourth year diving, he met Keith. 

Keith was everything Shiro’d ever been warned about. He was a beautiful spark of light in a world of black, with 8 glowing legs, sharp, ugly teeth and unseeing violet eyes. But more than that, Keith was interesting. 

Though he could not see, he could swim as fast as anything, navigating the black waters with abilities far stronger than sight. And he had the best stories. Stories of the monsters that live in the dark.

Not just theoretical stories, like Shiro’s mom had tried to frighten him with; Keith really knew what was down there. He had faced a shark that was all teeth and no body. He had wrestled with crabs 5 meters long. He had been chased by a colossal squid. 

Keith might be a little younger than Shiro, but he is the single most interesting mer Shiro has ever met. Year after year, just before Keith’s birthday, Shiro would swim down, down, down into the dark and meet Keith. There, they would race about so Keith could show Shiro his latest finds. Eventually, they’d wind their way to Keith’s home cave, where they would lie together in the sand and talk about everything and anything. 

It was a tight fit for Shiro to get in and out of Keith’s cave, and as he grew the cave became very cozy. But Keith was small, and his 8 legs had no bones to get in the way, so they always found a way to make it work. 

It’s a yearly tradition that Shiro takes to heart. But this year will be extra special. 

This year will be special, because last year something incredible happened. Last year, they had held hands as they swam. Last year, they had kissed when they said goodbye. Last year, they had sat beneath a roving herd of luminescent sea slugs and whispered sweet declarations of love to one another. 

For the past 12 months, Shiro has longed to dive into the dark to reunite with Keith. To hold Keith in his arms and share soft words, sweet kisses, and more. (The ‘more’ is particularly enticing, and Shiro has to admit to spending long hours thinking exactly how that ‘more’ might come about.) What stopped him from following through was the memory of Keith’s “see you next year” and the very practical fact that Shiro simply cannot find Keith’s cave without Keith himself leading him there. It is well hiding in the rocks, but in all honesty, Shiro won’t be able to even find the rocks in the dark. He needs Keith to get to Keith, and without a prearranged time and place, there is no way to find him. 

So, Shiro waited the long, lonely months for October to come around again, and now, on their arranged day, he races past the coral reef to the rocky drop off that leads to the dark waters. He has to start his journey at a particular peak, or else he might veer off course in the dark and Keith might never find him.

The journey is long, but Shiro speeds through it, watching the world around him grow dull, then dim, then dark. He lets his fingers graze the rockface as he swims, keeping him from going off course. 

At first Shiro’s eyes adjust to the dark, but the farther down he goes there is less to adjust to, until there is nothing else but blackness. He slows then; swimming only as fast as he dare. 

After a long while, a telltale glow blooms in the distance. Just a pinprick of light, at first, but as Shiro approaches it grows and blossoms like a flower, waving slowly in the deep-sea current. 

It’s Keith’s trademark: his way to catch a bite to eat when he’s too lazy to hunt. He lays on his back, with his 8 legs stretched out, moving with the current, his bioluminescence attracting the attention of his would-be-prey. Or, in this case, attracting the attention of his would-be-mate.

Shiro rushes forward, stopping just out of reach to shout their secret word; if the mer here doesn’t give the correct response, then Shiro is prepared for a fight. Keith gives his signals in return, and Shiro launches himself into Keith’s waiting arms. 

Immediately, Keith’s legs wrap around Shiro and hold him in a tight embrace, while Shiro buries his face in Keith’s neck.

“Missed you,” Shiro says, his voice muffled by how heavily his face is pressed to Keith’s neck and shoulder. 

“I missed you, too,” Keith echoes, his hands patting Shiro’s hair, before they drift over to touch at Shiro’s face. 

Keith’s fingers trace over Shiro’s face, and he murmurs a quiet “so handsome” to himself as he feels the sharp line of Shiro’s square jaw. 

His clever fingers draw up, and Shiro knows what Keith will see when he reaches Shiro’s nose. He shifts awkwardly in Keith’s embrace.

“So, what do you have to show me today?” he asks, hoping to distract Keith from his detailed perusal of his face. 

“I thought we could go-” Keith stops in his tracks as his fingers trace the edge of the scar. “Shiro? What’s this?” He traces the scar gently, following it from one cheek, over the bridge of Shiro’s nose, to the other. 

“It’s nothing,” Shiro insists. He shrugs, and immediately he knows that is the wrong move. 

In the glow cast by Keith’s legs, Shiro can see Keith’s face pull into a confused frown. One tentacle leg slips away from its hold on Shiro’s midriff and lifts up to his arm. Or – where his arm should be.

“Oh, Shiro…” Keith says in a low voice, thick with sorrow. His fingers caress Shiro’s cheek, “what happened?”

It wasn’t a big deal –that Shiro lost his arm in an attack. It didn’t bother him much. Not until this moment. Not until Keith touched him so gently and held him so tight. 

Suddenly, Shiro’s eyes are full of tears, and he takes a ragged breath. 

“Oh,” Keith says gently. He cups Shiro’s cheeks in his hands and gently presses kisses to Shiro’s cheeks and forehead, being mindful to protect Shiro from his sharp teeth. “Why don’t we go to my place and you can tell me about it?”

Shiro nods and they disentangle themselves. Keith shuts down his natural luminescence so that they aren’t easily followed, then he takes Shiro by the hand and leads him through the dark to his home cave.

The fit is tight as ever in Keith’s cave, with just enough room for Shiro to stretch out his fins and Keith to wrap along his side. Keith shifts a heavy rock over the opening, locking them in place, before he begins to glow again, and settles himself at Shiro’s side.

They’ve always lain close together in Keith’s cave – they’ve had to – but this time is different. Keith settles himself into the crook of Shiro’s arm and rests his head on Shiro’s chest like a pillow, while his legs lazily embrace Shiro from tip to tail. It’s intimate and deeply comforting. 

It feels like they’ve created their own private universe, lit by Keith’s tail (and their love, Shiro thinks, sappily). 

Without a word, Keith reaches across Shiro’s chest and touches lightly over the scarred remains of his arm. Keith’s unseeing eyes are filled with sadness on Shiro’s behalf.

Shiro sighed and watched his air bubbles float up and catch at the rock ceiling just above his head. “There was an attack. Zarkon sent his thugs to try and chase us out of our end of the coral. We fought them off, but they got my arm bad. We had to remove it.”

Keith’s sharp inhale of shock sounds loud in the enclosed space. His touch turns so light Shiro can’t tell if he actually _is_ touching him, or if it’s the movement of the water he feels against his skin. “Did it hurt?”

Shiro shifts uncomfortably and it buries him deeper into Keith’s embrace. “Not too bad. It would have been worse if Allura hadn’t been there. She was able to soothe the pain and heal the wound quickly with her magic.”

“I wish I had been there,” Keith says emphatically. “I would’ve protected you.” His legs wrap more firmly around Shiro’s body, holding him tightly – possessively. 

Shiro laughs at that. “You’d definitely give them a run for their money. Probably scare the gills off them, too.” He runs his thumb along the apple curve of Keith’s cheek, then touches lightly against one of Keith’s long, menacing, exposed teeth. “It’s too bad…”

He leaves the thought hanging, but he knows Keith understands; they’ve talked about this many times before. Shiro might be strong enough to face the crushing water pressure of the deep, but Keith does not have the constitution to swim up to the lighter waters. Every time he has tried, he has failed. 

Keith turns from Shiro’s touch but takes comfort in burying his face into Shiro’s neck. 

“I hate the thought of you getting hurt up there and there’s nothing I can do to stop it,” he says, his tone sulky. 

“And I hate the thought of something happening to you down here.”

Keith nods. 

They lay together listening to each other’s heartbeats for some time. Shiro rests his hand along the curve of Keith’s back and slowly draws his fingers back and forth. He has something he wants to talk to Keith about, but isn’t sure how to bring it up. He thinks Keith will like it, but he’s so nervous he can’t judge properly for himself. He waits a few more minutes, until he feels like he’ll burst if he doesn’t say it.

“Uh… Keith?”

Keith hums lazily in response. 

“I was thinking…” 

Shiro’s fingers freeze along Keith’s back as his nerves overtake him. With only a murmuring noise of encouragement, Keith touches Shiro’s hand lightly with one of his tentacles, urging Shiro to resume his slow touch. 

“… that… Well, you know how we always see each other once a year?”

Keith chuckles, creating a low rumble in his chest that Shiro can feel tremor across his skin. “Yes, I know.”

“Well, I was thinking we could stop that. _Imean!_” Shiro rushes to explain, “Not _stop_ stop! Just. I thought we could see each other more.”

“More sounds nice,” Keith agrees. His legs undulate around Shiro, shifting and readjusting their hold on him. 

“I thought I could stay down longer this time. Long as I can. And then, maybe I could come back after a week or two? Or a month. Whatever time you need.”

Keith’s hold tightens possessively again, holding tight for a few long moments before relaxing again. “I’d keep you here forever if I could,” he says. A tentacle traces over Shiro’s forehead, down his nose, and across his lips. “You’re too good looking to let you slip away.” 

It’s just a tease, Shiro knows that, but still it makes his heart flutter. He likes how well Keith thinks of him. Even when Shiro can’t think so well of himself, Keith thinks he’s perfect. It’s part of what makes Keith perfect. 

“Mmm, tell me more,” Shiro jokes.

“If I had my way, you’d never leave this cave,” Keith says. The tentacles around Shiro move around him again, shifting to wrap around Shiro’s tail, around his waist, and around his arm. Keith squeezes him lightly, not enough to actually bind Shiro, but enough that he feels held in place.

Shiro’s breath hitches in his throat as a spark of interest shoots through his gut. 

“You’d-” Keith interrupts himself and lifts his head as if he’s looking Shiro over. “Oh… you like that, huh?”

He can feel Shiro’s quickening pace, Shiro realizes, and he knows what it means.

The grip on Shiro’s wrist tightens experimentally and Shiro’s breath catches again. Keith’s lips split into a wide grin, revealing more sharp, evil looking teeth. “I’d keep you locked down here, fed and satiated, ready and waiting for me every day when I come home.” He tightens his grip on Shiro’s tail now, stretching Shiro’s body out as much as possible in the small space. “You’d belong just to me.” 

Keith moves Shiro’s hand to hold it over his head, making Shiro feel prone and vulnerable. Shiro’s heart pumps faster and faster as Keith slowly tightens around him. 

“Wha… What would you do to me?” Shiro asks. It’s hard to speak around the thick knot of desire that’s lodged itself in his throat.

Keith doesn’t answer right away. He drops his head in a slow, smooth motion and lightly drags his teeth along Shiro’s chest, just over his heart. “Everything you want,” he says darkly. 

Keith holds Shiro down at hips with his legs, letting the ends of his tentacles move slowly over his chest, his suckers tickling and teasing at Shiro’s skin. 

“I’ll hold you down and find every part of you that feels good.”

One sucker lands atop Shiro’s nipple and attaches itself firmly, tweaking Shiro’s nipple with the perfect amount of suction. Shiro groans so sharply it’s almost a yell. His whole body goes stiff with the pleasure and Keith uses that as an opportunity to strengthen his hold over Shiro, binding him properly. 

Shiro is much bigger than Keith, and just for his own curiosity he pulls at Keith’s tentacles to see if he can break free. He can’t.

He can’t move a single muscle.

He can’t even shiver with delight at the realization he is truly pinned. Keith is in complete control of him now. It’s delicious. It should be terrifying, but it just makes Shiro burn even hotter for Keith. 

He’s completely surrounded by Keith, now. He can feel him everywhere.

“I’ll learn what you like.” Keith’s hands smooth down Shiro’s sides, touching between the coiled tentacles, searching for the places that make Shiro’s heart race faster. “I’ll learn what makes you scream.” To illustrate his point, Keith twists over Shiro’s nipple again, ripping another sharp cry from Shiro.

Some of Keith’s touches, like the sucker on his nipple, and the scratch of teeth Keith draws along Shiro’s chest, are very strong. They walk that thin line between pleasure and pain – or, rather, they hop back and forth, alternating pleasure and pain until Shiro can no longer tell the difference. But some of Keith’s touches are so light, so soft, it seems impossible that Shiro can even feel them. 

One of Keith’s tentacles rubs lightly down Shiro’s delicate tailfin in slow, smooth strokes. Another curls gently through Shiro’s pelvic fins, playing with them. Keith’s hands are soft and comforting as they map out Shiro’s body. 

“Keith,” Shiro pants, “kiss me. Please.”

Keith doesn’t hesitate to comply. He shifts over Shiro, resting the weigh of his upper half on Shiro’s chest. It makes Shiro feel even more bound by Keith than before, and he groans, lifting his head as high as he can to reach Keith’s lips.

The kiss starts very cautious. Some of Keith’s fangs protrude past his lips, and they have to be careful not to shred Shiro’s lips in their fervor. As luck would have it, it turns out Shiro likes a bit of bite to his kiss, and his unabashed enthusiasm for Keith’s lips helps them find a rhythm that appeases their fiery desires. 

Keith continues to explore Shiro’s body as their kisses turn increasingly passionate. His hands and tentacles reach every inch of Shiro’s body, stroking and plucking at random to illicit deep, wanton moans from the strong mer. 

It’s so much. It’s nearly overwhelming. Shiro’s blood pumps through him like fire. He can feel every synapse in his body coming alive with burning desire. Shiro can feel his pouch start to tingle and fill.

Keith’s quick, smart fingers notice it at the same moment, and he brushes the back of his fingers lightly over Shiro’s bulging opening.

“What’s this?” Keith asks, rhetorically. At once, three tentacles start to worm across Shiro’s body, heading straight for that special spot. They stop just before they touch it, rubbing teasing strokes alongside the engorged slit. “Can I touch it, Shiro?” Keith whispers the request into Shiro’s ear.

Shiro groans. Like it’s not enough that Keith is absolutely rocking his world right now, pinning him tight and making Shiro feel things he never thought he could feel; no, he has to add being a gentleman to the list. 

“Mmmhmm,” Shiro moans, nodding sluggishly, all the while trying to will Keith’s tentacles to close that final inch and give him what he desperately needs. 

As one, all three tentacles move forward, almost touching Shiro exactly where he wants it, before pulling back. Keith’s hand curves around Shiro’s face and pulls him to look at Keith’s sightless eyes. “Nuh uh, Shiro. I want to hear you say it.”

“Please Keith,” Shiro asks, “Yes. Touch me, plea-ah!” Shiro’s words are cut off as three tentacles pry gently at his pouch. 

They touch him lightly, feeling the engorged flesh, and running quick touches along the seam of his slit. Then they press more firmly, massaging at the hidden, thickening flesh beneath. 

“Please, Keith, Please!”

“Right here?” Keith asks with fake innocence, pressing long and slow along the seam.

Shiro groans a mad, desperate noise and strains against Keith’s tight embrace. He tries to buck his hips further into Keith’s touch, but he can’t. He can’t move. But he needs it. He _needs_ Keith’s touch on him _now!_

Then Keith delicately pries Shiro open and slides a tentative tip into the warm pouch.

Shiro absolutely screams at the blinding pleasure of the intrusion. A moment later he finds his mouth stuffed full one with of Keith’s tentacles. It squirms in his mouth like a tongue and Shiro sucks on it, hard, to help relieve some of the incredible ecstasy burning through him. 

“Sh-Shiro,” Keith stutters.

It’s the first sign that Keith is losing his composure as well, and Shiro delights in the sound. He sucks again and begins to work the tentacle with his lips and tongue. “Feels good,” Keith mumbles.

Lower, Keith’s tentacle presses deeper into Shiro, finding Shiro’s curled cock and encouraging it out to play. Shiro is already thick and ready, and he unfurls quickly into the waters warmed by his and Keith’s body heat. 

Almost immediately, Keith wraps a tentacle around Shiro’s length and squeezes tight, milking Shiro for all he’s worth. Shiro screams again, and the tentacle in his mouth shivers against his lips in response. 

“Fuck, Shiro, you feel so good,” Keith praises. “God, I want to fuck you. Can I fuck you, Shiro? Say you’ll let me. Please, baby.”

Shiro wouldn’t dream of refusing Keith this request, but he can’t exactly answer with his mouth so full. So, he settles for sucking Keith _hard_ and nodding enthusiastically. He tries to say “yes please” around the tentacle and it results in a sharp hiss from Keith and an increased pressure all along Shiro’s body. 

Then everything moves around Shiro, the grip on him loosening and tightening as Keith reorganizes himself. He writhes around Shiro until one of his tentacles is free and he rubs this one over Shiro’s chest in long, heavy strokes. 

The glow on this leg is different from the others. Where the others are perfect circles of light, this one is lined with demi-circles, like each circle has been split down the middle.

Belatedly, Shiro realizes that this isn’t a leg. Though it moves the same as Keith’s other tentacles, this one is different: it’s Keith’s dick. 

Keith rubs his cock across Shiro’s chest, and lifts it to caress Shiro’s cheeks, before it dives down and begins to prod at the base of Shiro’s cock. It teases at the rim of Shiro’s pouch, stretched wide around his own cock. Just that is enough to get Shiro’s eyes rolling back in his head. 

Keith teases Shiro’s opening a while more, and then he gets to work in earnest. He pries Shiro open and delves in with the twitching, curious tip of his cock. 

The feeling is immediately overwhelming. Even alone, Shiro’s never bothered to touch his pouch once his cock was free and _boy_ was he ever missing out!! 

His pouch is warm and incredibly sensitive. He can feel every movement, every ridge of Keith’s cock as it moves inside him. When the suckers flex inside him (not sucking, just moving in rhythmic pulses) he feels such a wave of bliss overtake him he temporarily forgets his own name. 

Still, Keith keeps moving until Shiro is filled. He’s stuffed fit to burst with the whole length of Keith’s cock, wrapped around Shiro’s base. 

Once Shiro is full, Keith starts to retract and fill him again, pulsing in, out, and around Shiro. It takes a few minutes before Keith finds a proper rhythm, but once he does, it’s all over for Shiro. 

As Keith starts to fuck Shiro faster, his other tentacles (tentacles proper) start to twist and pull at Shiro’s cock again. Other’s still resume their exploration of Shiro’s most sensitive parts, plucking at his nipples and stroking at his fins. 

The tentacle in Shiro’s mouth backs off enough for Shiro to breathe, but still Shiro licks and sucks at it like he’s kissing Keith. 

Meanwhile, above him, Keith appears to be lost to his own pleasure. His head is tilted back and his mouth is slack-jawed. His eyes appear to be shut tight, and his entire body writhes with each pulse of his cock inside Shiro. His fingers pluck lightly at his own nipples, and what Shiro wouldn’t give to be able to do that himself right now!

But Shiro is still caught tight in Keith’s embrace, and he wouldn’t have it any other way.

“Shiro,” Keith gasps, thrusting himself faster into Shiro’s pouch. “Shiro. I’m gonna…. You feel so good, Shiro…”

“You feel amazing, baby,” Shiro reassures him. Though his words are slurred and nearly incomprehensible from the overwhelming high of Keith’s body, he’s sure Keith understands. 

Keith starts to tremble around Shiro, pulling them tight together, his cock starting to twitch so violently inside Shiro it almost vibrates. 

With a screaming, blinding, all-encompassing flash of pure bliss, Shiro comes. He spurts into the cave again and again, Keith’s tight grip milking him dry.

Still, Keith holds him tight. He’s immovable. And Keith continues to surge inside him, prolonging Shiro’s orgasm until he starts to worry it will never end. 

No sooner does Shiro think to himself that this is not a terrible way to die, than he feels Keith’s spine go rigid. Shiro’s pouch fills with Keith’s seed and it spills out into the cave to join his own. Keith rides his orgasm out for a few more shallow thrusts, and then he melts like jelly around Shiro. 

Though still wrapped around Shiro, head to tail, Keith’s grip is practically non-existent. He drops down to lay on Shiro’s chest and nuzzles into his pectoral. 

Suddenly freed, Shiro shifts and stretches, checking himself over. His shoulder is a little sore from being held over his head, but it’s nothing a good sleep wrapped around his mate won’t cure.

He settles himself down and closes his eyes; but he has one last thing to do before he can sleep. He takes Keith’s hand in his own and lifts it to his lips, covering each slender, skillful finger with a kiss.

“So, does this mean I can stay?”

Keith laughs weakly and folds his fingers between Shiro’s.

“Stay as long as you like, and then come back to me as quick as you can. I want as much of you as possible.”

**Author's Note:**

> I hope this feeds some of your tentacle desires for a bit! I know it's Keith tentacle-fucking Shiro again, but I like what I like, what can I tell ya? 
> 
> Also! I hope you liked that cat(fish) fucking joke because I literally thought of it while I was half-asleep the other morning and like JUMPED out of bed to add it into the story. 
> 
> In weirder news: this event is starting to do something to my brain. I was in a halloween store the other day and say a bull mask that normally would really creep me out and instead I thought about that fucking Carnival one I wrote with Shiro in the minotaur mask and my brain was like "kinda hot... maybe I should buy this?" Like wtf, brain. 
> 
> Tomorrow's another fucking weird one! Weirder than the scarecrow one? Who's to say! But I'm almost a little hesitant to post it, though I definitely still will because in truth I give 0 fucks. 
> 
> Shower me in compliments because I have a weekend of writing as much as fucking possible before I go on a week-long trip with my sister and the compliments help fuel my writing (and my massive ego!)
> 
> Follow me for fic updates:  
Twitter: [@WTuesdays](https://twitter.com/WTuesdays)  
Tumblr: [WatermelonTuesdays](https://watermelontuesdays.tumblr.com/)


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